1. Field of the Invention
The present invention relates to a sealing device and more particularly to a sealing device suitable for use in such locations as an engine crank shaft where it is required to prevent sand and dust from getting in through a gap between the rotating shaft and a housing and to prevent leakage of lubricating oil out through the gap.
2. Description of the Prior Art
A sealing device the construction of which is shown in FIG. 1 is known.
Referring to FIG. 1, a rotary shaft 33 is extended through a housing 31. A rotary member 30 is fixedly mounted on the rotary shaft 33. A seal ring 34 is fixed to the housing 31 via a fixed member 40. A seal lip portion 35 of the seal ring 34 contacts with a side surface 32 of an end portion of the rotary member 30, to allow a space A containing a fluid to be sealed including an oil, to be shut off from the atmospheric air B. The fixed member 40 and a hook-shaped portion 36 of the rotary member 30 form a narrow gap 37 therebetween. The fixed member 40 is provided in the surface thereof which is close to the seal ring with a groove 41 which is sunk inwardly with respect to the radius of the rotary shaft 33. In order to increase the sealability of the fixed member 40 and housing 31 with respect to each other, an O-ring 43 is provided in an annular groove 42 formed in a housing-contacting surface of the fixed member 40.
The sealing device of the above-described conventional construction has the following disadvantages.
(1) Since the fixed member 40 provided with the groove 41 is not rotated, the oil leaking out into the groove 41 from the sealed fluid-containing space A is not influenced by the centrifugal force while the oil stays in the groove 41, so that the leaked oil is not returned to the sealed fluid-containing space A at a high efficiency.
(2) This sealing device requires the fixed member 40 for supporting the seal ring 34 on the housing 31, and also the O-ring 43 for keeping the housing 31 and fixed member 40 sealed with respect to each other. This causes the construction of the sealing device to be complicated, and the manufacturing cost thereof to be increased.